In Act 3 Scene 3, What lines indicate the crisis, or the point-of-no-return of the play?

I think when Othello suspects Desdemona of infidelity. Actually Othello goes from not believing Iago to cursing his wife in a matter of a few stanzas,

She's gone. I am abused; and my relief

Must be to loathe her. O curse of marriage,

That we can call these delicate creatures ours,

And not their appetites!